Standing only between 4 and 16 inches (10 to 41 cm) tall, bright florets mostly hidden by the characteristic bract giving it the appearance of never opening flowers and with a life span of 5–6 weeks, the self-fertilizing Senecio vulgaris lives humbly among and occasionally under the other weeds and is easy not to notice.

Leaves and stems

Leaves of Senecio vulgaris grow directly from the stem, sessile or lacking their own stem (petiole), alternating in direction along the length of the plant, two rounded lobes at the base of the stem (auriculate) and sub-clasping above. Leaves are pinnately lobed and +2.4 inches (61 mm) long and 1 inch (25 mm) wide and get smaller as up the plant. Leaves are covered sparsely with soft, smooth, fine hairs. Lobes typically sharp to rounded saw-toothed.[3][4]

Open clusters of 8 to 10 small cylinder shaped rayless yellowflower heads ¼ to ½ inch (6 to 13 mm) with a highly conspicuous ring of black tipped bracts at the base of the inflorescence as is characteristic of many members of the genus Senecio.[3] There is a radiate form of Senecio Vulgaris, which is the result of cross pollination with the closely related Senecio Squalidus.[7]

Seeds

The name for the genus Senecio is probably derived from Senex (an old man), in reference to its downy head of seeds; "the flower of this herb hath white hair and when the wind bloweth it away, then it appeareth like a bald-headed man"[8] and like its family, flowers of Senecio vulgaris are succeeded by downy globed heads of seed. The seeds are achene, include a pappus[9] and become sticky when wet.[10] Laboratory tests have suggested maximum seed scattering distances of 2.1 and 3.2 yd (1.9 and 2.9 m) at wind speeds of 6.8 and 10.2 mph (10.9 and 16.4 km/h) respectively (affected by plant height)[6] suggests that it was more than wind that spread these groundsel seeds throughout the world.

The average weight of 1000 seeds is 0.21 gram (2,200,000 seeds per pound) and experienced a 100% germination success before drying and storage and an 87% germination success after drying and 3 years of cool dry storage.[11] In simple models for seed emergence prediction, soil thermal time did not predict the timing and extent of seedlingemergence as well as hydrothermal time[12][13] (warm rain).

Roots

The root system consists of a shallow taproot. This plant spreads by reseeding itself.[5]

Senecio vulgaris is a frost resistant[3] deciduous annual plant that grows willingly in disturbed sites, waste places, roadsides, gardens, nurseries, orchards, vineyards, landscaped areas, agricultural lands,[15] at altitudes up to 1,600 feet (500 m)[3] and is, additionally, self-pollinating[15] producing 1,700 seeds per plant with three generations per year.[22] Seeds are dispersed by wind and also cling to clothing and animal fur,[6] and as contaminates of commercially exchanged seeds; the relocation of this plant throughout the planet has been difficult if not impossible to contain.

As a plant that is reported to be both poisonous for human ingestion and also medicinal; much of the contradiction can be found by closely reviewing the words that are used and the dose (amount) of the poisonous substance that is ingested to prove either claim. All species of the genus Senecio contain pyrrolizidine alkaloids (e.g., senecionine) a substance that when a human has chronic exposure[54] can cause irreversible liver damage.[8][55]

Common groundsel as a medicinal herb does not seem to be recommended very often since 1931, when it was recommended as a diaphoretic, an antiscorbutic, a purgative, a diuretic and an anthelmintic, which was a demotion as it was previously suggested for the expelling of gravel of the kidneys and reins by Pedanius Dioscorides in the 70s-90s, for use as poultices by John Gerard in the late 16th century and as a cure for epilepsy by Nicholas Culpeper in the 17th century.[8] More current information is contradictory about the dangers of the ingestion of Groundsel. A heavily referenced paper from 1989 suggests that the response is immediate and gives pre-ambulatory care recommendations.[51] A Canadian poisonous plants information database references a paper from 1990 in presenting this prenatal warning: "In a case of prenatal exposure, a mother ingested tea containing an estimated 0.343 milligram of senecionine, resulting in fatal veno-occlusive disease in a newborn infant."[55] Information about the pyrrolizidine alkaloids, the substance present in Senecio vulgaris is much less contradictory and all warn of accumulation of the alkaloid.[56][57][58][59]

Certain pyrrolizidine alkaloids are non-toxic precursors that are converted to toxic metabolites in the body in a process called toxification[60]

Livestock

Linnaeus is cited to have claimed that "goats and swine eat this common plant freely, cows being not partial to it and horses and sheep declining to touch it, but not only are caged birds fond of it (the seeds), but its leaves and seeds afford food for many of our wild species (rabbits were given as an example)."[8] More recent studies claim that the lethal amount that cattle or horses need to consume is 7% of their body weight (example: 50 pounds (23 kg) would need to be consumed by a cow weighing 700 pounds (318 kg)). Lesser amounts cause the liver to lose function but is not apparent until the animal is stressed (by new feed or location, pregnancy, a different toxin, etc.). Sheep and goats have rumenbacteria that detoxify the alkaloids and are able to consume twice their body weight of this and other species of genus Senecio.[22][61] The alkaloids responsible are not destroyed by drying or by fermentation in silage.[6]

Introduced species become invasive when they compete with natives or with crops. Senecio vulgaris is not known to be a strong competitor but it has been known to reduce mint production.[62] There is evidence that it is not a strong invasive and sometimes protective of critically endangered native plants.[63]

Control

The approximately 22 millimetres (0.87 in) long[64]pappus seeds of Senecio vulgaris, each plant capable of producing 25,000 or more seeds (1,700 seeds per plant are more likely) with three generations of the plant per year;[22] seeds that are widely dispersed by the wind,[65] have been identified as a contaminant of cereal and vegetable seeds[3] and a poison to some livestock; there is some inspiration to understand the growth stages and determine some control methods.

Cultivation: Cultivation with the hand or tiller is a recommended method of controlling Senecio vulgaris from growing in gardens and planting fields; cultivate to a depth of 2 inches (51 mm). The plant does prefer to take root in disturbed soils, so cultivation rids new plants but also buries and stirs up new seeds so the cultivation needs to be repeated at 14-day intervals.[6] Seeds can still mature even when the plant has been killed;[50] seed from plants cut in flower had germination levels of 35%. Groundsel seed numbers increased in soil during a 2-year set-aside left fallow but not when there was a sown grass cover. The weed cannot live on grazed, trampled or mowed sites.[6]

Biological: The pathogenrust fungus or Puccinia lagenophorae and the Cinnabar mothTyria jacobaeae have both been used and studied in an attempt to control infestation of Senecio vulgaris.[66] One study showed that rust fungus infected Senecio vulgaris survived and actually used more of the available soil nutrients.[67] The cinnabar moth eats groundsel between June and August, but the seeds germinate and the plant grows as soon as the ground is warm enough (and after a warm rain),[12] making this an insufficient control almost everywhere groundsel can be found.[22]